dm: blk: Tidy up obtaining a block device from its parent

This function now finds its block-device child by looking for a child
device of the correct uclass (UCLASS_BLK). It cannot produce a device of
any other type, so drop the superfluous check.

Provide a version which does not probe the device, since that is often
needed when setting up the device's platdata.

Also fix up the function's comment.

Signed-off-by: Simon Glass <sjg@chromium.org>

3 files changed, 43 insertions, 13 deletions

diff --git a/drivers/block/blk-uclass.c b/drivers/block/blk-uclass.c
index e82789f4a3..38800a3115 100644
--- a/drivers/block/blk-uclass.c
+++ b/drivers/block/blk-uclass.c
@@ -508,24 +508,28 @@ ulong blk_derase(struct blk_desc *desc, lbaint_t start, lbaint_t blkcnt)
 	return blk_erase(desc->bdev, start, blkcnt);
 }
 
-int blk_get_from_parent(struct udevice *parent, struct udevice **devp)
+int blk_find_from_parent(struct udevice *parent, struct udevice **devp)
 {
 	struct udevice *dev;
-	enum uclass_id id;
-	int ret;
 
-	device_find_first_child(parent, &dev);
-	if (!dev) {
+	if (device_find_first_child_by_uclass(parent, UCLASS_BLK, &dev)) {
 		debug("%s: No block device found for parent '%s'\n", __func__,
 		      parent->name);
 		return -ENODEV;
 	}
-	id = device_get_uclass_id(dev);
-	if (id != UCLASS_BLK) {
-		debug("%s: Incorrect uclass %s for block device '%s'\n",
-		      __func__, uclass_get_name(id), dev->name);
-		return -ENOTBLK;
-	}
+	*devp = dev;
+
+	return 0;
+}
+
+int blk_get_from_parent(struct udevice *parent, struct udevice **devp)
+{
+	struct udevice *dev;
+	int ret;
+
+	ret = blk_find_from_parent(parent, &dev);
+	if (ret)
+		return ret;
 	ret = device_probe(dev);
 	if (ret)
 		return ret;
diff --git a/include/blk.h b/include/blk.h
index c8cbb64c7f..1db203c1ba 100644
--- a/include/blk.h
+++ b/include/blk.h
@@ -454,9 +454,35 @@ int blk_next_free_devnum(enum uclass_id uclass_id);
 int blk_select_hwpart(struct udevice *dev, int hwpart);
 
 /**
+ * blk_find_from_parent() - find a block device by looking up its parent
+ *
+ * All block devices have a parent 'media' device which provides the block
+ * driver for the block device, ensuring that access to the underlying medium
+ * is available.
+ *
+ * The block device is not activated by this function. See
+ * blk_get_from_parent() for that.
+ *
+ * @parent: Media device
+ * @devp: Returns the associated block device, if any
+ * Returns: 0 if OK, -ENODEV if @parent is not a media device and has no
+ * UCLASS_BLK child
+ */
+int blk_find_from_parent(struct udevice *parent, struct udevice **devp);
+
+/**
  * blk_get_from_parent() - obtain a block device by looking up its parent
  *
- * All devices with
+ * All block devices have a parent 'media' device which provides the block
+ * driver for the block device, ensuring that access to the underlying medium
+ * is available.
+ *
+ * The block device is probed and ready for use.
+ *
+ * @parent: Media device
+ * @devp: Returns the associated block device, if any
+ * Returns: 0 if OK, -ENODEV if @parent is not a media device and has no
+ * UCLASS_BLK child
  */
 int blk_get_from_parent(struct udevice *parent, struct udevice **devp);
 
diff --git a/test/dm/blk.c b/test/dm/blk.c
index 35bd5318f0..6f0cb98c86 100644
--- a/test/dm/blk.c
+++ b/test/dm/blk.c
@@ -160,7 +160,7 @@ static int dm_test_blk_get_from_parent(struct unit_test_state *uts)
 	ut_assertok(blk_get_from_parent(dev, &blk));
 
 	ut_assertok(uclass_get_device(UCLASS_I2C, 0, &dev));
-	ut_asserteq(-ENOTBLK, blk_get_from_parent(dev, &blk));
+	ut_asserteq(-ENODEV, blk_get_from_parent(dev, &blk));
 
 	ut_assertok(uclass_get_device(UCLASS_GPIO, 0, &dev));
 	ut_asserteq(-ENODEV, blk_get_from_parent(dev, &blk));